1. Field of the Invention
The present invention relates to a thin plate supporting container clamping device on which a thin plate supporting container is placed for automatically unloading thin plates such as semiconductor wafers, memory disks, or liquid crystal glass substrates stored in the thin plate supporting container at a destination.
2. Description of the Related Art
The thin plate supporting container clamping device is a device for fixing the thin plate supporting container to a loading port. In other words, the thin plate supporting container clamping device is a device for fixing the thin plate supporting container that is transported to a clean room with a plurality of semiconductor wafers or the like stored therein to the loading port for automatic unloading or loading thereof.
The thin plate supporting container clamping device includes a hook member provided on an upper surface of the loading port so as to move in the vertical direction, and supports the thin plate supporting container on the upper surface of the loading port by engaging and retracting the hook member with a retaining portion of the thin plate supporting container.
A force of the hook member to engage and retract with the retaining portion of the thin plate supporting container is set to such a magnitude that a container body is not displaced when a lid member of the thin plate supporting container is automatically removed.
However, with the thin plate supporting container clamping device in the known art as described above, since the hook member is pulling the thin plate supporting container with the force of such a magnitude that the container body is not displaced when the lid member is automatically removed, the pulling force may be too strong for the container body after having removed the lid member. When the pulling force is too strong, the container body may be deformed, and hence the semiconductor wafers stored therein may deviate from height alignment. When the semiconductor wafers deviate from height alignment, there may arise a problem such that a portion of a fork of a device for unloading and loading the semiconductor wafers comes into contact with the semiconductor wafers, whereby the semiconductor wafers may be scratched or cracked.